Imaging of Pelvic Floor Dysfunction

Abstract

The pelvic floor, which is divided into anterior, middle, and posterior compartments, receives support from muscles, endopelvic fascia, and ligaments that support the pelvic organs and prevent organ prolapse. Deficiency in the musculofascial support system leads to pelvic floor dysfunction with a wide range of symptoms such as urinary incontinence, fecal incontinence, organ prolapse, and dyspareunia. Imaging has an established role in evaluating pelvic floor dysfunction. Imaging modalities range from conventional imaging, such as fluoroscopic defecography and dynamic colpocystography, to ultrasound and magnetic resonance imaging. Magnetic resonance defecography is particularly useful as it helps to detect multicompartmental involvement, which helps in meticulous surgical planning. This article provides an initial review of pelvic floor anatomy, followed by the role of imaging to assess disorders in each pelvic compartment.

 

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Keywords

pelvic floor - compartment - prolapse - defecography

Introduction

Pelvic floor dysfunction refers to disorders resulting from weakened musculofascial support to the pelvic floor. It usually affects women over 50 years old. Other risk factors are obesity, multiparity, pregnancy, smoking, and connective tissue disorders. The symptoms of pelvic floor dysfunction are varied, ranging from urinary and fecal incontinence, straining to void, to dyspareunia and organ prolapse.

 

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Pelvic Floor Anatomy

The female pelvic floor has three anatomic compartments. The anterior compartment comprises of the bladder and urethra, the middle compartment, which contains the uterus and vagina, and the posterior compartment, which includes the rectum and anal canal ([Fig. 1]).[1] [2]

Fig. 1 Pelvic compartments. T2-weighted high-resolution sagittal magnetic resonance imaging (MRI) image through the pelvis shows anterior, middle, and posterior compartments, demarcated by white dashed lines. UB, urinary bladder; Ut, uterus; R, rectum.

The pelvic floor consists of the musculofascial layer that provides passive and dynamic support to the pelvic organs in each pelvic compartment. The pelvic floor comprises three layers from cranial to caudal: endopelvic fascia, pelvic diaphragm, and perineal membrane or urogenital diaphragm.[1]

 

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Endopelvic Fascia

The endopelvic fascia is the connective tissue network beneath the peritoneum that supports pelvic organs. The endopelvic fascia wraps around organs and provides passive support to the bladder, vagina, and uterus. Fascial condensations and ligaments offer additional support in each of the pelvic compartments.

In the anterior compartment, these include pubocervical fascia formed by endopelvic fascia, which connects the bladder and anterior vaginal wall to the pubis.[3]

The urethral supporting ligaments, namely, the periurethral, paraurethral, and pubourethral ligaments, support the urethra.[1] In addition, a hammock like support to the urethra is provided by the anterior vaginal wall and endopelvic fascia.[2]

In the middle compartment, the uterus and vagina are suspended to lateral pelvic wall by the parametrium superiorly containing the uterosacral and cardinal ligaments and paracolpium more inferiorly. Three levels of endopelvic fascial support to vagina have been described by DeLancey.[3] [4]

• Level I: endopelvic fascial support suspends the upper portion of the vagina and uterine cervix to uterosacral ligaments and ischial spines.

• Level II: endopelvic fascial support is to posterior wall of the urinary bladder and mid-portion of the vagina.

• Level III: endopelvic fascia supports the lower portion of the vagina and attaches it to the perineal membrane. It also includes the urethral suspensory ligaments.[2] [3]

In the posterior compartment, rectovaginal fascia, attached to the perineal body, is located between the anterior rectal wall and posterior vaginal wall.[1] Posterior support comes from the uterosacral ligaments, which are paired fascial condensations inserted on the sacrum ([Fig. 2A] and [B]).

Fig. 2 (A) T2-weighted high-resolution axial magnetic resonance imaging (MRI) image through the vagina and urethra shows anterior vaginal wall provides a hammock-like support to the urethra (red arrow). (B) T2-weighted high-resolution axial MRI image through the pelvis delineates uterosacral ligaments, which provide posterior support to the uterus and cervix (red arrow).

Lateral support: Arcus tendinous fascia pelvis is the attachment of the endopelvic fascia laterally on pelvic sidewalls, providing lateral support.[2]

 

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Pelvic Diaphragm

The pelvic diaphragm represents the middle layer of the pelvic floor, comprising the levator ani and coccygeus muscles.[5]

Levator Ani

The levator ani serves as the primary mechanism for pelvic support, with its attachments to the pubis and the arcuate tendon levator ani laterally on both sides. It helps to maintain continuous contraction even at rest, which helps to sustain pelvic floor tone and avert pelvic organ prolapse (POP).[4] The main components of the levator ani include iliococcygeus, puborectalis, and pubococcygeus.

 

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Iliococcygeus

It fans out laterally with inferior concavity, extending from external anal sphincter (EAS) medially to get attached to the pelvic side wall at the posterior part of the arcus tendinous.

The condensation of the muscle posteriorly, anterior to the coccyx, forms the levator plate or anococcygeal ligament ([Fig. 3A] and [B]).

Fig. 3 (A and B) T2-weighted high-resolution coronal and axial magnetic resonance imaging (MRI) image through inferior pelvis shows the fibers of iliococcygeus, the largest muscle of levator ani, which fans out laterally to the pelvic wall with inferior concavity (red arrows in A and in B).

 

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Pubococcygeus

It arises from the superior pubic ramus with its insertion into the arcus tendinous.[6] Based on their connections to the urethra, vagina, anus, and rectum, the medial fibers of the pubococcygeus are classified as pubourethralis, pubovaginalis, puboanalis, and puborectalis, collectively referred to as pubovisceralis.[7] The puborectalis muscle is shaped like a “U,” originating from the pubic bones at the front and forming a sling around the rectum.[8] The contraction of the pubococcygeus muscle effectively closes the anorectal and urogenital hiatus, providing support during rest and increased intra-abdominal pressure ([Fig. 4]).

Fig. 4 T2-weighted high-resolution axial magnetic resonance imaging (MRI) image through inferior pelvis shows fibers of the pubococcygeus (blue arrow) and puborectalis (yellow arrow).

 

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Ischiococcygeus

It plays a lesser role in supporting the pelvic floor, stretching from the ischium to the coccyx.[4]

 

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Urogenital Diaphragm

The perineal membrane, also known as the urogenital diaphragm, constitutes the caudal-most layer of the pelvic floor.[4] This structure is formed by connective tissue and the deep transverse peroneus muscle. It spans horizontally between the ischial rami, reaching the perineal body and the EAS.

It serves as an attachment point for various structures, including the endopelvic fascia, the EAS, the urogenital diaphragm, the bulbocavernosus muscle, and the puborectalis muscle.

The anterior section of the perineal membrane includes the compressor urethrae and urethrovaginal sphincter muscles. In contrast, the posterior section connects the vagina and perineal body to the bony pelvis through transverse fibrous bands of connective tissue.[5]

 

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Role of Imaging

Imaging helps to detect involvement of multiple pelvic compartments and to plan treatment, especially when surgical intervention is required.

 

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Ultrasound

Ultrasound (US) evaluation of the anterior and middle pelvic compartments is critical in assessing pelvic floor disorders. Translabial or transperineal US with two-dimensional, three-dimensional (3D), or four-dimensional techniques provides a detailed view of these compartments' anatomical structures and functional dynamics ([Fig. 5A]). For anterior compartment evaluation, US is a more reliable modality than magnetic resonance imaging (MRI).[9]

Fig. 5 (A) Transperineal ultrasound, midsagittal scan shows distended urinary bladder, U demarcates urethra, V demarcates vagina, and S demarcates pubic inferior margin of symphysis. (B) Transperineal ultrasound, midsagittal scan shows distance from bladder neck to pubic symphysis (yellow dotted line) at rest and during Valsalva maneuver (C) .This was seen to be 2.3 cm at rest and 1.46 cm during Valsalva maneuver, indicating some descent of bladder neck during Valsalva maneuver.

 

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Ultrasound Evaluation of Anterior Compartment

The anterior compartment primarily consists of the bladder and urethra. During translabial US examination, the patient is positioned in the dorsal lithotomy position.[9] [10] A midsagittal transperineal scan is performed with a 3.5- to 7-MHz curved array transducer.[10] The US assessment begins with the patient at rest, during which measurements are made to determine the residual bladder volume (RBV) and bladder wall thickness. The RBV is calculated by incorporating the two largest diameters of the bladder, which reveal insights into the functionality of the bladder.[9]

Bladder Neck Descent

This is assessed by measuring the distance between the lowest margin of the pubic symphysis and the bladder neck at rest and maximal Valsalva maneuver. This provides a quantitative assessment of bladder neck descent, which may indicate urinary incontinence ([Fig. 5B] and [C]). In general, a descent greater than 30 mm is common in women experiencing incontinence.[9]

 

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Urethral Hypermobility

This is assessed by measuring the posterior urethrovesical or retrovesical angle (β). This is the angle between a line through the urethral axis and the line through the trigonal surface of the bladder, and varies from 90 to 120 degrees normally. This may increase to 160 to 180 degrees with urethral hypermobility.[10]

 

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Funneling of Bladder Neck

This may be seen with urethral hypermobility and can lead to stress incontinence. Bladder neck funneling can be demonstrated at rest and during Valsalva. Color Doppler can be used to illustrate urine leak with Valsalva.[10]

 

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Ultrasound Evaluation of Middle Compartment

The middle compartment includes the uterus and vagina. Attention is paid to the cervix and the vagina during the scan. US imaging helps to identify any abnormal descent of the cervix or the presence of conditions such as uterovaginal prolapse. The maximum descent of these structures during the Valsalva maneuver is measured against the inferior margin of the pubic symphysis, which serves as a line of reference.

3D imaging helps assess the levator ani muscle integrity and the visualization of avulsion tears, which occur after childbirth, and dynamic 3D US is useful for pre- and postoperative evaluations, especially regarding surgical mesh placements.[9]

 

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Fluoroscopic Defecography

Fluoroscopic defecography (FD), also known as fluoroscopic evacuation proctography, remains the best imaging to evaluate symptoms of obstructed defecation. This study involves filling the rectum with radio-opaque barium paste, approximating stool consistency. Rectal filling initiates the defecatory process, which is under voluntary control.

FD involves both static and dynamic imaging to evaluate anatomical and functional abnormalities causing obstructed defecation, such as rectocele, intussusception, or prolapse, perineal descent, anismus, and cul-de-sac hernias.[11] The examination is conducted in three phases—preevacuation, evacuation, and postevacuation, and utilizes specific pelvic landmarks and measurements to characterize abnormalities.

Steps Prior to Fluoroscopic Defecography

Bowel preparation is recommended in the form of a rectal cleansing enema at home.

Void prior to procedure. The steps of the procedure are clearly explained to the patient.

Steps taken to ensure privacy.[11]

 

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Technique

• The patient is positioned in the left lateral position

• Digital rectal exam (DRE) may be performed using lidocaine hydrochloride, although DRE is not mandatory

• Rectum is filled with barium (150 mL of 100% w/v barium sulfate diluted with 400 mL of water) till there is the urge to defecate

• Vaginal opacification is also recommended

• Enteric contrast is recommended to demonstrate enteroceles, although this is not mandatory

• Enteric contrast to be ingested 60 to 90 minutes prior to performing the FD

• The bladder may be filled with contrast when specifically requested

• When all three compartments are filled, the study is called a cystocolpoproctogram

• The patient is then positioned in a left or right lateral position on a radiolucent commode

(A) Resting Phase

A static lateral spot radiograph is obtained while the patient is at rest. The image should encompass the pubic symphysis, sacrum, coccyx, perineal region, and anal canal, including skin markers if applied. An adequate inferior field-of-view is necessary to visualize pelvic floor descent during subsequent dynamic maneuvers.[12] [Fig. 6] shows images obtained during maneuvers mentioned below.

Fig. 6 Fluoroscopic defecogram – standard images obtained at (A) rest and during various maneuvers ((B) squeeze, (C) strain, (D) defecation).

 

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(B) Pelvic Floor Contraction (Kegel Maneuver-Squeeze)

A spot or cine image is acquired while the patient performs a maximal voluntary contraction of the pelvic floor muscles (“squeeze”). Adequate instruction and patient coaching are essential to ensure proper technique and capture the full range of pelvic floor elevation.

 

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(C) Straining (Valsalva Maneuver) Without Evacuation

The patient is instructed to strain without expelling rectal contrast. This phase is recorded using either cine or spot imaging to assess pelvic floor descent. This step may be omitted in patients with known or suspected fecal incontinence to avoid inadvertent rectal contrast evacuation.[13]

 

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(D) Evacuation Phase

Cine fluoroscopy is used to record active defecation. The sequence may be repeated if effort is inadequate or incomplete emptying is observed. Patients may be allowed to use their customary defecatory techniques (e.g., adjusting posture or applying perineal pressure) to facilitate rectal emptying and reveal dynamic abnormalities such as rectoceles or intussusception.

 

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(E) Postevacuation Strain

Following complete rectal evacuation, a final static image is acquired during maximal straining following a pelvic floor contraction. The patient is instructed to perform a vigorous strain immediately after a Kegel maneuver. This allows assessment of the full extent of organ descent and can help identify abnormalities such as POP or enterocele that may be obscured by retained contrast during earlier phases.[13]

 

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MRI Defecography—Techniques and Protocols

Patient Instructions

No specific bowel preparation is required before imaging. Solid oral feeds are avoided 2 hours prior, and sips of clear fluid till the procedure. A partially filled urinary bladder is desirable; patients are instructed to void 1 hour before the appointment and then advised to have a liter of fluid.

Maintaining a good rapport and ensuring patient privacy are vital. Care must be taken to elicit recent rectal surgeries or procedures in the past 8 weeks and exclude allergies to lignocaine. The procedure and maneuvers are explained in the patient's preferred language in a well-understood manner ([Box 1]). After ensuring the patient understands the instructions, they are made to practice these maneuvers a few times before being taken onto the MRI gantry.

Box 1 Making patients understand the instructions and the maneuvers

Squeeze: “Imagine yourself in a crowded room, and you may pass flatus; what would you do to stop that?” Strain: “Try to push the gel without expelling it.” Defecate: “Try to push the gel out in a single go”

The patient is positioned in the left lateral position with knees flexed, and one knee is drawn to the chest. After informing the patient, approximately 5 mL of 2% lignocaine gel is gently instilled into the rectum. After a wait of at least 3 to 4 minutes for the lignocaine to act, a soft, wide caliber (24–26 G) rectal catheter or flatus tube is used to instill 150 to 200 mL of US gel into the rectum until the patient develops a rectal sensation.[12] [13] The patient is positioned supine with a pillow underneath the knee and legs mildly apart after draping them with an incontinence pad and instructed to hold gel until further instructions. Insisting on performing the maneuvers without moving in the gantry is essential. [Table 1] shows the MRI sequences and phases of image acquisition and the image parameters.[12]

Table 1 Pelvic floor MRI protocol for 1.5T[12]

Sequence	Imaging planes	TR (ms)	TE (ms)	Slice thickness	Matrix	FOV (mm)	Number of slices
T2 FSE	Sagittal	2500–6000	80–94	5, 1	384 × 384	280	Up to 50
T2 FSE	Coronal	2500–6000	80–94	5, 1	384 × 384	280	Up to 50
T2 FSE	Axial	2500–6000	80–94	5, 1	384 × 384	280	Up to 50
TRUFISP CINE	Midsagittal (in rest, squeeze, strain, and defecation)	47–48	1.2–1.4	7, 10	216 × 240	320	Up to 20

Abbreviations: FOV, field of view; FSE, fast spin echo; MRI, magnetic resonance imaging; TE, time to echo; TR, time to repeat; TRUFISP, true fast imaging with steady-state precession.

 

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Measurements

All the measurements are made in the midsagittal plane in single-shot/TRUFISP CINE images. The anorectal angle is measured between the long axis of the anal canal and the posterior wall of the rectum just above the anorectal junction. In normal resting and squeezing phases, due to the resting tone of the puborectalis and levator ani muscles and their contractions during the squeezing phase, the anorectal angle is near the right angle or acute. Due to the relaxation of the pelvic floor during the straining and defecating phases, the anorectal angle widens. [Table 2] gives the normal anorectal angle during the different maneuvers.[13] [Table 3] shows the definitions of the lines and their normal and abnormal measurements.[13] The reference points for anterior, middle, and posterior compartments are the posterior and most inferior aspect of the urinary bladder base, the anterior and most inferior aspect of the cervix or posterosuperior vaginal apex (post-hysterectomy), and the anterior aspect of the anorectal junction, respectively, as depicted in [Table 4].[13]

Table 2 Normal anorectal angle during rest, squeeze, strain, and defecation[13]

Maneuvers	Demonstration	Reference ranges
Rest		100–127 degree
Squeeze		Decreases by 15–20 degree (85–107 degree)
Strain		Increases by 5- 20 degree (105–147 degree)
Defecation		Increases by 5 to 40 degrees (105 -167 degree)

Table 3 Lines and measurements[13]

Lines	Image demonstration	Description	Reference range	Pathological grading
Pubococcygeal line (PCL)		Inferior border of pubic symphysis to the last coccygeal joint (corresponds to levator muscle plane)	Pelvic organs should be cranial to the line
H line		Inferior border of the pubic symphysis to the posterior wall of the rectum at the level of the anorectal junction. (corresponds to the anteroposterior diameter of hiatus)	Normal < 6 cm	Mild: 6–8 cm Moderate: 8–10 cm Severe: > 10 cm
M line		Perpendicular line from the posterior wall of the rectum at the level of the anorectal junction to the pubococcygeal line (corresponds to pelvis hiatus descent)	Normal < 2 cm	Mild: 2–4 cm Moderate: 4–6 cm Severe: > 6 cm

Table 4 Reference points in anterior, middle, and posterior compartments[13]

Compartment	Image demonstration	Description
Anterior		Posterior and most inferior aspect of the urinary bladder base
Middle		Anterior and most inferior aspect of the cervix
Posterior		Anterior aspect of the anorectal junction

 

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Grading Pelvic Organ Prolapse with MRI

MRI assessment utilizes two key anatomical lines:

• Pubococcygeal line (PCL): Extends from the inferior border of the pubic symphysis to the last coccygeal joint, representing the pelvic floor level.

• Midpubic line: Aligns with the long axis of the pubic symphysis and corresponds to the vaginal hymen level.

The “rule of three” is applied in MRI-based grading, where organ descent (reference point in each organ) below the PCL is classified as:

• Mild: Less than 3 cm

• Moderate: 3 to 6 cm

• Severe: More than 6 cm

MRI of Anterior Compartment

The anterior pelvic compartment comprises the bladder and urethra.

Cystocele – The term “cystocele” refers to the descent of the bladder base more than 1 cm below the PCL. This is caused by a tear in the pubocervical fascia or levator ani muscle. The distance of the bladder base below the PCL is used to grade cystocele into mild, moderate, or severe[1] [9] ([Table 4]). Cystoceles may displace the uterus and anorectal junction posteroinferiorly, with widening of H and M lines ([Fig. 7]). It may also bulge into the anterior vaginal wall causing eversion of vaginal mucosa.[9]

Fig. 7 Cystocele. Magnetic resonance (MR) defecogram – dynamic phase of defecation shows cystocele where the reference point in urinary bladder (red arrow) is below the pubococcygeal line (white dashed line). There is also an anterior rectocele, shown by a yellow arrow.

Urethra – The urethral sphincter helps to preserve urinary continence by the mucosal seal, compression by extracellular matrix, collagen, urethral smooth, and striated muscle, and periurethral support by ligaments and neural control. The urethral muscle and urethral supporting ligaments are visualized on MRI, best seen on T2-weighted high-resolution images. The urethra has a target-like appearance with hypointense mucosa and submucosal layers, hyperintense middle smooth muscle layer, and hypointense outer striated muscle layer.[14]

The urethral supporting ligaments are seen as continuous hypointense bands. These include the periurethral ligaments, which course anterior to the urethra, the paraurethral ligaments, which arise from the lateral wall of the urethra, the periurethral ligaments, and the pubourethral ligaments between the urethra and the arcus tendinous laterally.[1] The urethra on T2-weighted midsagittal MRI is seen as a retropubic, hypointense structure with a vertical axis in the resting state and straining.[2]

 

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Urethral Sphincter Deficiency

Thinning of the striated sphincter muscle with increasing age can cause flattening of the posterior urethral wall and result in intrinsic sphincter deficiency.[2] [14] This may ultimately lead to funneling of the bladder neck, which is the widening of the proximal urethra at the bladder neck at rest or straining, and can lead to stress incontinence.

 

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Urethral Hypermobility

This refers to the change of normal vertical urethral axis toward a more horizontal plane by a clockwise rotation of more than 30 degrees during straining, when there is raised intra-abdominal pressure ([Fig. 8]). This is seen on sagittal MR images during dynamic phase of MR defecography and is a cause of stress incontinence.[9]

Fig. 8 Urethral hypermobility. Magnetic resonance (MR) defecogram – dynamic phase of defecation shows urethral mobility (yellow arrow) where the normal vertical axis of the urethra now has a more horizontal deviation. The red arrow demarcates a small peritoneocele.

 

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MRI of Middle Compartment

POP involves the descent of pelvic organs due to weakened support structures. The middle compartment, comprising the uterus, cervix, and vagina, is stabilized by the pubocervical fascia, rectovaginal fascia, parametrium, and paracolpium. MRI plays a crucial role in evaluating these structures and determining the severity of prolapse.[2]

 

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Uterine and Vaginal Vault Prolapse

Uterine prolapse ([Fig. 9]) refers to the downward displacement of the uterus resulting from weakened support. MRI assesses the extent of prolapse by measuring the perpendicular distance from the most anteroinferior part of the cervix (reference point) to the PCL:

Fig. 9 Uterine prolapse. T2-weighted high-resolution sagittal magnetic resonance imaging (MRI) image through the pelvis shows uterine prolapse with marked descent of the uterus and cervix in resting state, below the pubococcygeal line (white dashed line).

• Mild prolapse: Descent less than 3 cm below the PCL

• Moderate prolapse: Descent between 3 and 6 cm below the PCL

• Severe prolapse: Descent exceeding 6 cm below the PCL[1]

In post-hysterectomy patients, posterosuperior vaginal apex is used as the reference point. This should remain 1 cm above the PCL.[1]

 

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Vaginal Support and Fascial Defects

The vagina is supported at three levels, as described by DeLancey, with specific MRI findings associated with defects at each level:

• Level 1 defect: Loss of uterosacral ligament support leads to bilateral vaginal wall sagging, known as the “chevron sign.”

• Level 2 defect: Loss of arcus tendinous support disrupts the H-shape of the vagina, and also results in posterior bladder wall bulging, termed the “saddlebag sign.”

• Level 3 defect: Weakening of urethral suspension ligaments causes widening of the retropubic space, producing the “moustache sign.”[2]

 

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Pathologic Conditions Related to Pelvic Floor Weakness

Weakness in the middle compartment often coexists with pelvic floor relaxation. MRI differentiates true prolapse from enterocele, peritoneocele, and sigmoidocele. Enterocele, involving peritoneal content herniation, is well-visualized due to superior soft-tissue contrast.[5] Post-hysterectomy damage to the paracolpium increases apical prolapse risk.[15]

 

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Posterior Compartment Imaging—MRI and Fluoroscopic Defecography

The posterior compartment contains the rectum and anal canal. The iliococcygeus muscle, along with the rectovaginal fascia, forms a diaphragm that supports the organs in the posterior compartment. The puborectalis muscle, creating a U-shaped sling between the pubis and anus, tightens the urogenital hiatus to maintain pelvic organ position. Damage to the perineal body, such as during an injury like episiotomy in vaginal childbirth, or disruption of the rectovaginal fascia or iliococcygeus muscle, can cause bowel or peritoneal contents to protrude leading to posterior prolapse.[14]

Both fluoroscopic and MR defecography are valuable to study pelvic floor anatomy and the dynamics of rectal emptying. It is particularly useful when recreating the act of defecation is necessary, especially in patients with obstructed defecation symptoms, complex pelvic floor, and defecatory disorders.[11]

 

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Descending Perineum Syndrome

On defecography, this is seen as abnormal caudal motion of the anorectal junction with strain, relative to a fixed reference point, usually the PCL. It can be quantified by the M line, which measures the descent of the posterior aspect of the anorectal junction from the PCL. An M line measuring more than 2.5 cm indicates pelvic floor descent. It is usually associated with elongation of the H line, which represents widening of the anteroposterior diameter of levator hiatus, and caudal angulation of the levator plate.[1] The levator plate can be identified easily on the midsagittal MR image appearing parallel to the PCL at rest. It is a good index of the muscular tone and elasticity of the pelvic floor. Angulation of more than 10 degrees caudally relative to the PCL indicates pelvic floor weakness ([Figs. 10] and [11A]).[15] It can be associated with rectoceles, intussusception, prolapse, etc.

Fig. 10 Widened pelvic hiatus and descent of pelvic floor. Magnetic resonance (MR) defecogram – dynamic phase of defecation shows marked widening of pelvic hiatus as demarcated by the elongated H line (yellow dashed line) and pelvic floor descent, shown by the elongated M line (red dashed line). The white line represents the pubococcygeal line.

Fig. 11 (A) Descending perineum syndrome. Fluoroscopic defecogram image shows marked descent of the anorectal junction below the pubococcygeal line (white line). (B) Anterior rectocele. Fluoroscopic defecogram image shows bulge of the lower anterior rectal wall, size demarcated by red line drawn perpendicular to the line through the central axis of the anal canal (white line).

 

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Rectocele

Anterior rectocele is bulge of the lower anterior rectal wall measured by drawing a perpendicular line from the line drawn through the central axis of the anal canal to the anterior rectal wall ([Fig. 11B]). Rectoceles are graded as: small - < 2 cm; medium - 2 to 4 cm; and large - > 4 cm.[1]

 

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Anismus

Anismus, also known as pelvic floor dyssynergia, is a functional disorder characterized by inappropriate contraction of the puborectalis muscle. There is nonrelaxation of the anal sphincter and in its more severe form, there may be paradoxical increased puborectalis contraction during strain or evacuation. On conventional and MR defecography, there is lack of descent of the pelvic floor during defecation, prominent puborectal impression, and inadequate widening of the anorectal angle (acute anorectal angle) with incomplete evacuation and long interval between opening of the anal canal and the start of defecation ([Fig. 12]).[1] [11]

Fig. 12 Anismus or puborectalis dyssynergia. Fluoroscopic defecogram images show inadequate widening of the anorectal angle (outlined in red) during rest (A), straining (B) and evacuation (C), with a persistent acute anorectal angle.

 

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Rectal Intussusception

Intussusception is invagination of the rectal wall's full thickness (mucosa and muscular layer) into the rectum (intrarectal), anal canal (intra-anal), or beyond the anus (true complete external rectal prolapse) ([Fig. 13]). Description is based on the position of the apex of the intussusceptum in the rectum or anal canal.[11] MR defecography offers the advantage of distinguishing between mucosal intussusception (nonobstructing) and full-thickness rectal intussusception, which is crucial for planning surgical treatment. Simple mucosal prolapse may be managed with transanal excision of the prolapsed mucosa, while full-thickness rectal invagination might require rectopexy.

Fig. 13 Rectal intussusception with prolapse. Fluoroscopic defecogram images show invagination of the rectal mucosa with filling defect in the rectum and anal canal and leading to mucosal prolapse (red arrows).

 

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Enterocele, Sigmoidocele, and Peritoneocele

In healthy individuals, rectovaginal space located below the upper third of the vagina is supported by pelvic ligaments and iliococcygeus muscle and thus closely apposed. Widening of the rectovaginal space can result in herniation of the peritoneal fat, small bowel, sigmoid colon, and fluid into the pouch of Douglas. An increased risk of enterocele may be present when there is disruption of the rectovaginal fascia by hysterectomy ([Fig. 14]).[15]

Fig. 14 Enterocele. Fluoroscopic defecogram images show marked inferior descent of the opacified small bowel loops during dynamic phase of defecation (red arrows).

 

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Conclusion

Pelvic floor weakness, often involving multiple compartments, can occur with or without prolapse and may require surgical intervention. A thorough evaluation of the pelvis is essential before considering surgery. MRI offers a noninvasive method for assessing the pelvic floor and is widely used in clinical practice. Currently, FD or dynamic cystocolpoproctography and dynamic MRI are performed together as complementary techniques. For a complete evaluation of POP severity, radiological findings should be correlated with the patient's clinical symptoms.

 

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Conflict of Interest

None declared.

• References

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Publication History

Article published online:
19 August 2025